Electric oil well heater



Oct. 21, 1952 F COLBY ELECTRIC OIL WELL HEATER Filed March I5, 1950 K 5 E 7 \l Y 7 m A. 0 C 3 8 0 D g a 9 Q Q 0 6 6 6 2 w I Q o O O O O O O 0 O O c F O Q Q Q Q 0 0 0 0 0 m o m a G 0 a I I W. mm 5 a IN V EN TOR.

S Y E N m T T A Patented Oct. 21, 1952 TED STATES PATENT OFFICE The invention relates to a heating device to be inserted in a flow string of an oil well, and more particularly to a heat exchanger to heat a localized area of flow in a string of pipe and to create an intimate contact between the oil flowing through such string and the heater.

One of the primary disadvantages with heating devices for use in an oil well to eliminate solid paraflin from the oil flowing in a string of pipe in a well, is that such devices distribute the heat over too large an area of pipe. This prevents heating of any portion of the fluid flow through the pipe to a sufflcient temperature, whereby the solid parafiin may be eliminated and also due to the large amount of pipe which is normally heated any heat in such pipe is quickly dissipated in the oil.' Therefore if the rate of flow of oil is even moderately slow'such rate is too fast to impart enough heat into the oil to reduce any solid paraffin therein into liquid form.

A primary object of the instant invention is to provide a device for heating a localized area of fluid flow in a string of well pipe to a sufficient temperature whereby the solid paraflin in the oil flowing through such localized area will be eliminated therefrom.

Another object of the invention is to provide a device for eliminating solid paraffin from the oil flowing in a string of well pipe by creating a turbulence in a localized area, whereby intimate contact is effected between the oil and a heating coil placed in the area.

Still another object of the invention is to provide in a device for eliminating solid paraffin from the oil flowing in a string of well pipe, a hollow cylindrical housing, a perforated liner through which the oil flows, and a heating element on said liner, electrical conduits extending down through the housing and connected to the heating element, to heat such element, said liner having flow passages extending laterally therethrough whereby oil passing through such liner is circulated outwardly and around said element to intimately contact the flowing oil and element in a localized area of flow.

A further object of the invention is to provide a heat exchanger wherein fluid is intimately contacted with a heating element or coil.

A further object of the invention is to provide a heat exchanger wherein fluid is intimately contacted with a heating element or coil said heat exchanger being so constructed and arranged that a minimum of heat is transmitted to the pipe in which the device is positioned.

Still another object of the invention-19w provide in a heating device which is to be positioned through which the oil flows, said element being perforated and having heating coils on the Deriphery thereof whereby oil flowing through said element may be heated to remove the solid parafiin from the oil, the perforations in said element acting to pass the oil flowing through the element outwardly and around the element whereby intimate contact between the oil and the heating coils is eifected.

Other and further objects and advantage of the invention will become more readily apparent from a consideration of the following description and drawings, wherein:

Fig. 1 is a vertical sectional view of a portion of a well bore showing the flow string of the oil well in elevation with the device secured. in the flow string, and

Fig. 2 is a vertical sectional view partially in elevation showing an enlarged portion of the heater and the details of construction.

In Fig. 1 of the drawings, a well bore is indicated at 2,- having the usual casing 3 extending longitudinally of the well bore. Disposed within the casing 3 is the tubing 4 which is provided with suitable connections 5 and 6 whereby the oil from the producing formation may be conducted to various tanks.

Secured in the casing at some suitable height in the well bore is the heat exchanger device denoted generally by the numeral 1 comprising the present invention. Fig. 1 shows only one of such devices mounted in the tubing. It should be noted that one or more of these devices may be mounted in the tubing at various elevations in the well bore depending upon the particular conditionin each well. However, for purposes of illustration, there is shown only one of such devices in the tubing of the drawing.

The device 1 may be secured by any suitable means in the tubing, such as by welding or by a threaded connection between the ends of the devices Band 9 and the tubing 4.

In Fig. 2 the device 1 is shown as comprising a hollow elongated housing or body H in which is mounted the perforated liner or element 13. The element 43 is preferably hollow, and may be concentrically arranged within the housing or body I I and extends longitudinallyof such housing. It is to be noted that the hollow element [3' serves as a conduit for the flow of oil through the heat exchange device.

The element [3 is'preferably' of a smaller diameteftha'ii tiiebody of housin I l whereby a pas;-

sage I5 is formed between the inner wall I6 of the body or housing I I and the outer periphery I! of the element I3. Spiral heating coils I8 are provided on the outer periphery I 9 of the element I3. The heating elements or coils I8 are of a high resistance, low conductivity type material whereby electrical energy supplied through the conduit connected through the housing or body I I at 2| and secured to the coil at 23 effects heating of such coils. The conduit 20 extends upwardly and out of the well bore as shown at 24 in Figure 1 whereby suitable surface control may be provided (not shown).

The element I3 is provided with perforations 25 or lateral passages extending preferably throughout the length thereof and arranged between the spirals of the heating coil I8. The perforations or lateral passages 25 provide a means of communication between the interior of the heating element I3 and body or housing II. However, these perforations are made obliquely in the heating element, with some of them slanting upward and some downwards.

The purpose of the oblique slant of these perforations is to encourage fluid to pass into and out of the passage or cavity between the element I3 and housing II, and thus pass directly over and around the heating coils. In this manner the liquid or gas passing through the tubing or pipe line in which the unit is assembled is intimately contacted with the heating element and heater.

As oil flows upwardly through the tubing and through the element I3, which extends for a portion of the length of the tubing, it is heated in the localized area where the perforated liner is positioned. The oil flows outwardly through the perforations 25 and into the chamber or passage I5 and thence back into the element I3. This creates a turbulence in the localized heating area and effects an intimate contact between the coils and the oil flowing through the string of pipe.

While it is believed that the operation of the invention is apparent from a reading of the foregoing description, the following is given by way of further amplification and illustration.

Some oils carry an appreciable amount of parafiin-like substances. These substances remain in solution as long as the temperature of the fluid is above their melting point. As the oil leaves the sand its temperature is usually well above the melting point of these parafiins. In its passage upward through cooler strata heat is lost from the flowing column. When the temperature of the flowing column becomes lower than the melting point of the paraflins they solidify and either adhere to the wall of the tubing or cause trouble at the well-head. Temperatures low enough to allow the paraffin to solidify are usually not found much below 2000 feet. This device would therefore logically be placed at that level in a well which is slightly below the first evidence of paraffin deposit on the tubing wall. The heat loss as the fluid rises through the cooler strata is not constant, but it is a simple procedure to calculate the amount of heat which would have to be added when the surface temperature of the oil, the rate of flow, the capacity of the heat exchanger and other factors are known.

One or more of the devices I can be spaced at various elevations in the tubing string or flow string of an oil well. Suitable surface controls are connected to one end of the electrical conduit 24 with the other end being secured through the housing or body II and to the heating coil I8 spirally mounted on the outer periphery I 9 of the element I3.

As oil flows through the flow string it comes in contact with the perforated liner I3. It is to be noted that the area of the heating is 10- calized with respect to the total height of the oil column present. In this manner, a greater amount of heat can be dissipated within a smaller area than if the same amount of heat were distributed over the total column. This serves to heat the oil in such area to a sufliciently high temperature whereby the solid paraffin therein is eliminated. As the oil flows upwardly through the element I3 it will pass out through the perforations or lateral passages 25 in such heating element and into the chamber I5 formed between the element I3 and housing or body I I. This will create turbulence and a slowing down of the rate of flow in and around the localized heating area which effects a more intimate contact between the oil flowing through the heated area and the element I3. This turbulence increases the total amount of surface area of oil which comes in intimate or direct contact with the heating coils and improves the efliciency of the device. This is true because while the oil column as compared to the heating element has a low conductivity, the conductivity of the oil column, in effect, is increased because more surface area of the oil is exposed to the heating element. Or, in other words, since more surface area of the oil is exposed to the direct heating action of the heating coils by turbulence and the slower rate of flow in and around the perforated liner, the effective thickness of column being heated is correspondingly reduced.

As the oil continues its turbulent flow in the chamber I5 up around the perforated liner or element I3, it will be discharged back into such element adjacent the top 30 thereof.

From the foregoing description it can be readily seen that a heating device is provided which creates a turbulence and slows the rate of flow in a localized area of the flow string.

Particular attention is directed to the invention in that due to the increase in diameter of the housing II over the diameter of the pipe above and below, the flow is slowed as it passes through the unit allowing more time for the exchange of heat from the heating element to the fluid.

It is to be also noted that while the invention is described as applying particularly to the removal of paraffin from oil wells, it can also be used in surface pipe lines to prevent freezing, and to keep the viscosity of heavy oils down to where they will flow freely either in an oil stream in a well or a pipe line. It can also be used to keep the temperature of flowing oil sufficiently high to keep bothersome hydrates in solution.

The device can also be readily adapted for sulphur mining. One or more of the units can be placed at the bottom of the steam line in a sulphur well as a source of primary heat, to eliminate the expensive surface boiler system now in use. It can be used in the same manner in conjunction with the present boiler system as a super-heater for steam-which has been forced into the line from above. Such a heater will make it possible to recover sulphur economically at far greater depths than the present Fraasch system will allow.

Th device of course can be provided with suitable controls to operate it either intermittently or continuously, depending upon the particular conditions in the flow string in which, it is used.

The invention also aids in the removal of paraffin substances from a flow string, because as a general rule, heavier hydro carbons are soluble in lighter hydro carbons. Therefore, as the oil flows through the heat exchanger the lighter elements of the oil will tend to separate by the increase in temperature. There will, therefore, be a chemical solution of the parafiin substances by contact with these light fractions of the oil in addition to the heating and removing of such paraffin substances as herein previously discussed.

Broadly the invention contemplates an apparatus for creating turbulence and slowing the rate of flow in a localized area of a well bore or other pipe line and for heating the fluid flowing through such localized area of a pipe.

What is claimed is:

1. A device for eliminating solid paraflin from the oil flow in a string of well pipe and for eradicating accumulated parafiin from such pipe comprising, a closed hollow cylindrical housin means to secure said housing to the flow string, a hollow element in said housing and connected at each end to the flow string, said element being of substantially the same diameter as the flow string and extending longitudinally in said housing and spaced from the cylindrical side walls of said housing to provide a passage for oil flow, spiral heating coils secured to the outer periphery of said element, an electrical conduit connected through said housing and into said coils, said element having perforations between said spiral coils and extending throughout the length of said element whereby the oil passing through the flow string passes through and around said element and into said passage between said element and said housing to provide intimate con- 6 tact between said heating coils and the oil in said flow string.

2. A device for eliminating solid parafiin from the oil flow in a string of well pipe by creating a turbulence and slowing down the rate of flow in a localized area whereby intimate contact is eifected between the oil and a heating element placed in the areacomprising, a closed hollow cylindrical housing, means to secure said housing to the flow string, a hollow cylindrical element secured in said housing and connected to the flow string, said element being concentric with and extending longitudinally of said housing and spaced from the cylindrical side walls of said housing to provide a passage for oil flow around said heating element, spiral heating coils secured to the outer periphery of said element, an electrical conduit connected through said housing and into said coils, said element having perforations between said spiral coils and extending throughout its length to provide egress and ingress for the flow of oil from the interior of said element to the passage between said housing and element whereby the oil is intimately contacted with said element in a localized area of flows as it flows through the well string to eliminate solid parafiin from such oil.

FRED COLBY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 965,287 Gardner -1. July 26, 1910 1,082,971 Pick Dec. 30, 1913 1,309,721 Drinkern July 15, 1919 1,672,200 Buck June 5, 1928 2,208,087 Somers July 16, 1940 2,276,833 Germain Mar. 17, 1942 2,512,226 Edwards June 20, 1950 

